SUNConferences, 17th Annual Conference of the Rapid Product Development Association of South Africa

Font Size: 
EFFECT OF HEAT TREATMENT ATMOSPHERE ON FORMATION OF ALPHA CASE IN TI6AL4V PRODUCED BY ADDICTIVE MANUFACTURING FOR BIOMEDICAL APPLICATION.
Shyline Tafadzwa Chingowo

Last modified: 2016-10-06

Abstract


Ti6Al4V high strength to density ratio makes it ideal for biomedical application but formation of alpha case during heat treatment compromises this strength .During the heat treatment process, oxygen diffuses into the titanium resulting in formation of an oxide scale on the metal. A hard and brittle oxygen enriched layer known as “alpha case” is later formed beneath the scale. The alpha case is fragile, thus limiting the biomedical application of Ti6Al4V. Therefore, the formation of alpha case must be prevented during heat treatment. The objective of this project is to study the effect of heat atmosphere on alpha case formation during the heat treatment of Ti-6Al-4V. The alloy was annealed in an argon environment at 940 O C   for 2 hours. Microstructural evolution in the samples were studied by optical microscope. The thickness of alpha case was measured using the ACT-2U software in microscope.  The as heat treated Ti6Al4V samples showed grains of primary alpha in a matrix of transformed beta (retained beta) with a thin layer of alpha case on the surface. The results indicated that heat treatment in argon atmosphere resulted in the formation alpha case. This could probably be due to higher hydrogen and oxygen pick up in the argon furnace.